1. Field of the Invention
The present invention relates to a manufacturing method of an electroluminescence (EL) element. More particularly, the invention relates to a manufacturing technique of an EL element of forming color changing media (CCM) without using a lithographic process.
2. Description of Related Art
An EL element is an organic EL element or an inorganic EL element. The organic EL element is a self-emitting type element emitting light by electrically exciting a fluorescent organic compound. This element is characterized by a high luminance, a high-speed response, a high viewing angle, face emission, and a thin thickness, and this element can emit light in multiple colors. Further, this element has a feature that it is a fully solid element emitting light through DC impression of a low voltage of a few volts, and fluctuation of properties is slight at low temperature. Since the EL element using an organic substance as a light emitting material can easily cover the entire visible range through adoption of a structure which may consist of a combination of a light emitting layer and color changing media and selection of a material forming the light emitting layer and color changing media, efforts are actively made for application to a full-color flat panel display. Known methods for full-color application of the EL element include, for example, a method of color-changing a white emission (the white emission/color changing method) and a method of color-changing a blue emission (the blue emission/color changing method).
When manufacturing a structure adopting the white emission/color changing method or the blue emission/color changing method for full-color application of the EL element, however, it is the conventional practice to form color changing media, and to perform patterning via a lithographic process into a shape corresponding to pixel regions. Formation of the color changing media on a substrate by using the lithographic process causes much waste of the color changing media material, leading to a higher manufacturing cost. The necessity of photosensitivity for the color changing media material results in a smaller range of material selection. Further problems include a high running cost of facilities necessary for the lithographic process and a larger equipment space.
The EL element is expected to be applicable to full-color flat panel displays in the future, as shown in FIG. 6, and the reduction of the manufacturing cost is an indispensable prerequisite.
The present invention was developed in view of the aforementioned problems and has an object to provide a method of manufacturing an electroluminescence element which may consist of a light emitting layer and color changing media for manufacturing color changing media without using a lithographic process, and to provide a high-performance electroluminescence element manufacture by this method.
A first manufacturing method of an electroluminescence element of the present invention may consist of the steps of causing a light emitting layer to emit light by applying a desired voltage between an anode and a cathode, with the light emitting layer in between, and obtaining visible rays by wavelength-converting the emitted light using color changing media formed in individual pixel regions. This method may further consist of a first step of forming partitioning members having openings corresponding to the pixel regions on a substrate, a second step of discharging a color changing media precursor into the openings using a liquid discharge head, and a third step of forming color changing media by solidifying the color changing media precursor discharged onto the substrate.
Particularly, in the above-mentioned first method, the second step should preferably be a step of discharging the color changing media while adjusting the doping ratio of color changing constituents of the color changing media.
The color changing media precursor is a precursor of color changing media selected from the group consisting of red color changing media, green color changing media and blue color changing media. In this case, the precursor of the red color changing media should preferably have a chemical composition which may consist of any one of a cyanine-based pigment, a pyridine-based pigment, a xanthene-based pigment and an oxadine-based pigment.
The precursor of the red color changing media may adopt a chemical composition prepared by dispersing: (a) a rhodamine-based fluorescent pigment, and (b) a fluorescent pigment, which absorbs rays in the blue region and induces energy transfer or re-absorption to the rhodamine-based fluorescent pigment, into a light transmitting medium. The precursor of the green color changing media may have a chemical composition which may consist of, for example, a stilbene-based compound and a coumarin-based compound. The precursor of the blue color changing media may have a chemical composition which may consist of, for example, a coumarin pigment.
In the aforementioned first method, a light emitting layer should preferably be formed by coating or by vapor deposition so as to form an upper layer relative to the color changing media after the above-mentioned process of forming the color changing media (the third step).
A second manufacturing method of an electroluminescence element of the invention may consist of the steps of causing a light emitting layer to emit light by applying a desired voltage between an anode and a cathode with the light emitting layer in between, and obtaining visible rays by wavelength-converting the emitted light using color changing media formed in individual pixel regions. This method may further consist of a first step of forming anodes at positions corresponding to the pixel regions on a substrate, a second step of forming partitioning members which partition between the anodes, and have openings at positions corresponding to the pixel regions, a third step of discharging a precursor of the color changing media into the openings using a liquid drop discharge head, and filling the anodes with the precursor of the color changing media, and a fourth step of forming the color changing media by solidifying the precursor of the color changing media.
Particularly, in the above-mentioned second method, the third step should preferably be a step of discharging the precursor of the color changing media while adjusting the doping ratio of color changing constituents of the precursor of the color changing media.
The precursor of the color changing media is conductive and is a precursor of color changing media selected from a group consisting of red color changing media, green color changing media and blue color changing media.
In the aforementioned second method, a light emitting layer should preferably be formed by coating or by vapor deposition so as to form an upper layer relative to the color changing media after the above-mentioned process of forming the color changing media (the fourth step).
The contact angle between a material composing a nozzle surface of the liquid drop discharge head and the precursor of the color changing media should preferably be within a range from 30 to 170 deg. The precursor of the color changing media should preferably have a viscosity within a range from 1 to 20 mPas. Further, the precursor of the color changing media should preferably have a surface tension within a range from 20 to 70 dynes/cm. The liquid drop discharge head should preferably comprise a pressurizing chamber substrate having a pressurizing chamber which stores the color changing media precursor and a piezo-electric thin film element attached to a position permitting application of a pressure to the pressurizing chamber.
Further, according to the invention, the electroluminescence element for causing a light emitting layer to emit light by applying a desired voltage between an anode and a cathode arranged with the light emitting layer in between, and obtaining visible rays by wavelength-converting the emitted light with color changing media formed for each of pixel regions, may consist of the color changing media between the anode and the cathode. The electroluminescence element has, for example, a lamination structure comprising a cathode, a light emitting layer, color changing media and an anode. Particularly, the color changing media is conductive and is color changing media selected from the group consisting of red color changing media, green color changing media and blue color changing media.